Like lkpi_pci_get_domain_bus_and_slot() implement lkpi_pci_get_slot()
using pci_find_bsf() instead of pci_find_dbsf() (no domain).
This is needed for a wireless driver.

Unfortunately the name [pci_get_slot()] collides with the native PCI
function. Add a guard around it and disable the use when the native
version is required (in lkpifill_pci_dev() and in bnxt/bnxt_en; if the
latter gets fixed we can probably also fix work around it in the former;
further conflicts in drm-kmod 6.1-lts, 6.6-lts, and master were resolved).

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